Feedthrough apparatus with noble metal-coated leads

FIELD OF THE INVENTION

The present invention relates to electrical devices that incorporate electrical feedthroughs, and to their method of fabrication. More particularly, the present invention relates to improving the conductivity of metal leads that are part of electrical feedthroughs, and also improving their connectivity with conductive contacts.

BACKGROUND OF THE INVENTION

Electrical feedthroughs serve the purpose of providing a conductive path extending between the interior of a hermetically sealed container and a point outside the container. The conductive path through the feedthrough comprises a conductor pin or terminal that is electrically insulated from the container. Many such feedthroughs are known in the art that provide the conductive path and seal the electrical container from its ambient environment. Such feedthroughs typically include a ferrule, and an insulative material such as a hermetic glass or ceramic seal that positions and insulates the pin within the ferrule. Electrical devices such as biorhythm sensors, pressure sensors, and implantable medical devices (IMD's) such as pulse generators and batteries often incorporate such feedthroughs. Sometimes it is necessary for an electrical device to include a capacitor within the ferrule and around the terminal, thus shunting any electromagnetic interference (EMI) at high frequencies at the entrance to the electrical device to which the feedthrough device is attached. Typically, the capacitor electrically contacts the pin lead and the ferrule.

Some of the more popular materials that are used as a feedthrough terminal are susceptible to oxide growth, which can act as an insulator instead of a conductor over the surface of the pin lead, particularly if the oxide growth is extensive. For instance, during fabrication of a feedthrough/capacitor combination the central terminal is subjected to one or more heat treatments. Even though feedthroughs are typically manufactured in an inert atmosphere, high temperatures will encourage oxidation if there is residual oxygen from a sealing gas or from dissociation of surface adsorbed water on fixtures and components. Oxidation of the terminal affects the conductivity of the pin lead and its ability to make good electrical connections with other elements. The ability for the surface oxidized pin terminal to be electrically connected to a contact would be particularly impaired if mechanical means such as crimping were employed to establish an electrical connection. This impairment is troublesome in cases where mechanical means might be less time consuming or less costly than other joining methods such as welding.

Accordingly, it is desirable to provide a method of manufacturing an electrical apparatus incorporating a feedthrough device wherein mechanical means are employed to establish an electrical connection between the feedthrough leads and a contact of the electrical apparatus. In addition, it is desirable to provide a feedthrough device that can be utilized in such a method. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.

SUMMARY OF THE INVENTION

A medical device is provided that is efficiently manufactured. The medical device comprises an encasement, an electrical device disposed within the encasement, an electrical contact coupled to the electrical device, and a feedthrough assembly. The feedthrough assembly comprises a ferrule extending through the encasement and having an inner surface, a terminal extending through the ferrule and having a first end extending into the encasement, a conductive metal coating that is more resistant to oxidation than the terminal covering the first end of the terminal, and a body of insulation material disposed between the terminal and the inner wall for preventing the ferrule from electrically contacting the terminal. The medical device also comprises a connector for electrically coupling the first end to the electrical contact.

A feedthrough assembly is also provided that includes the feedthrough described above, and a connector that is connected to a first end of the feedthrough assembly terminal for electrically coupling the first end of the terminal to an electrical contact.

Also, a method of manufacturing a medical device is provided. The method comprises the steps of deploying an electrical device within an encasement, the electrical device being coupled to an electrical contact, and forming the above-described feedthrough assembly in the encasement. Then, the first end of the feedthrough assembly terminal is electrically coupled to the electrical contact using a connector.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and

<figref idrefs="DRAWINGS">FIG. 1</figref> is a sectional view of an electrical feedthrough that hermetically seals and electrically connects with a contact by way of a conductive metal-coated terminal, where the electrical connection is made using a mechanical joining device, according to an embodiment of the present invention;

<figref idrefs="DRAWINGS">FIG. 2</figref> is a sectional view of an electrical feedthrough that hermetically seals and electrically connects with a contact by way of a partially conductive metal-coated terminal, where the electrical connection is made using a mechanical joining device, according to an embodiment of the present invention;

<figref idrefs="DRAWINGS">FIG. 3</figref> is a sectional view of an electrical feedthrough that incorporates a capacitor and hermetically seals and electrically connects with a contact by way of a conductive metal-coated terminal, where the electrical connection is made using a mechanical joining device according to an embodiment of the present invention;

<figref idrefs="DRAWINGS">FIG. 4</figref> is a cross sectional view of a crimping apparatus electrically coupling a noble metal-coated terminal to an electrical contact according to an embodiment of the invention.

<figref idrefs="DRAWINGS">FIG. 5</figref> is a cross sectional view of a spring connection electrically coupling a noble metal-coated terminal to an electrical contact according to one embodiment of the invention.

<figref idrefs="DRAWINGS">FIG. 6</figref> is a cross sectional view of an electrical feedthrough that hermetically seals and electrically connects with a first contact by way of a conductive metal-coated terminal, and with a second contact by way of a conductive metal-coated ferrule, where both electrical connections are made using mechanical joining devices according to an embodiment of the present invention; and

<figref idrefs="DRAWINGS">FIG. 7</figref> is an isometric view of a medical device incorporating the electrical feedthrough illustrated in <figref idrefs="DRAWINGS">FIG. 6</figref>.

DETAILED DESCRIPTION OF THE DRAWINGS

The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.

Referring now to <figref idrefs="DRAWINGS">FIG. 1</figref>, there is depicted one embodiment of an electrical feedthrough <b>100</b> which is intended for use in conjunction with an electrical device, an exterior container <b>40</b> of the electrical device being in contact with the feedthrough <b>100</b>. The term “electrical device” used hereafter refers to any device incorporating an electrical feedthrough, including but not limited to biorhythm sensors, pressure sensors, and various IMD's such as pulse generators and batteries. Although the discussion of the feedthrough device throughout the specification is directed to devices employing glass-to-metal, ceramic-to-metal, or ceramic-to-metal polymer type seals, it is to be understood that the principles of the invention are of general application to any feedthrough utilizing a pin lead for the purpose of making electrical connection to any contained electrical device which is to be sealed from its ambient environment. The principles of the invention are also applicable to multiple pin feedthroughs.

The feedthrough <b>100</b> of the present invention includes a center pin terminal <b>12</b>, with a portion of the length of the terminal <b>12</b> passing through a ferrule <b>10</b>. Electrical feedthroughs that are used in IMD's and other biological devices may inadvertently come into contact with body fluids. Thus, it is desirable that the terminal <b>12</b> be made of a bio-stable material. For example, the terminal <b>12</b> may consist of or include niobium, titanium, tantalum, and alloys of the metals, and other bio-stable conductive metals. Preferably, the terminal <b>12</b> is manufactured using a refractory metal. In a typical installation, one end of the terminal <b>12</b> extends through a capsule or container <b>40</b> into the interior <b>15</b> of the electrical device, and electrically connects with at least one internal contact <b>34</b>. Another end of the terminal <b>12</b> extends to the exterior <b>25</b> of the electrical device.

The insulating material <b>14</b> surrounds a portion of the length of the terminal <b>12</b>. In an exemplary embodiment of the invention, the insulating material <b>14</b> includes glass or glass-ceramic joined directly to conductor materials by heating or a ceramic joined to conductor materials by braze material by heating, or high dielectric polymers such as polyimides. If the insulating material is a ceramic material, the material is preferably ruby, sapphire or polycrystalline alumina. The composition of the insulating material <b>14</b> should be carefully selected to have thermal expansion characteristics that are compatible with the terminal <b>12</b>. The insulating material <b>14</b> prevents a short circuit between the terminal <b>12</b> and the ferrule <b>10</b> or the container <b>40</b>.

In order to ensure a tight seal between the glass <b>14</b> and the walls of the container <b>40</b>, the ferrule <b>10</b> is disposed as a thin sleeve therebetween. Typically the ferrule <b>10</b> has an annular configuration, but may have any configuration suitable for use with the container for the electrical device. The ferrule <b>10</b> may be formed of titanium, niobium, tantalum, zirconium, any combination thereof, or any other suitable metal or combination of metals. The ferrule <b>10</b> is affixed to the inner surface of the container <b>40</b>, preferably by welding although any other suitable means, such as gluing or soldering, may be used.

In order to prevent oxide formation on the terminal <b>12</b> and the contact resistance instability attributed to such oxide formation, the terminal <b>12</b> is coated with a thin film <b>30</b> of a conductive metal that is less easily oxidized than the terminal <b>12</b>. Preferably, the conductive metal film <b>30</b> comprises a noble metal or an alloy of noble metals. The noble metals include gold, platinum, palladium, rhodium, ruthenium, and iridium. These metals and alloys thereof are highly resistant to oxidation, and consequently protect the terminal <b>12</b> from hot, humid, or even liquid environments. The protection provided by the noble metals and alloys thereof decrease the contact resistance, and therefore increase the stability of crimp connections between a contact and the terminal <b>12</b>. The conductive metal film <b>30</b>, hereinafter referred to as the noble metal film <b>30</b>, is applied by DC magnetron sputtering or RF sputtering in an exemplary embodiment of the invention, although other conventional techniques may be used such as chemical vapor deposition, cladding, vacuum depositing, painting, other types of sputtering, etc. The noble metal film <b>30</b> is deposited at a minimum thickness of about 100 Å, and preferably is at a thickness ranging from about 3000 Å to about 7000 Å.

In an exemplary embodiment of the invention, an intermediate film <b>13</b> may be deposited on the terminal <b>12</b> prior to deposition of the noble metal film <b>30</b>. The thin intermediate film <b>13</b> is a refractory metal, preferably titanium or niobium, and enhances the adhesion of subsequent metal depositions to the terminal <b>12</b>. The intermediate film <b>13</b> is applied by any conventional technique such as sputtering, chemical vapor deposition, vacuum depositing, painting, or cladding, and is preferably applied using either DC magnetron sputtering or RF sputtering.

According to the embodiment of the invention depicted in <figref idrefs="DRAWINGS">FIG. 1</figref>, the noble metal film <b>30</b> coats the regions of the terminal <b>12</b> that are both within and outside the feedthrough device <b>100</b> in a continuous manner. The manufacturing process for this embodiment includes the step of coating the terminal <b>12</b> with the noble metal film <b>30</b> using an appropriate technique prior to forming the hermetic seal between the insulating material <b>14</b> and the terminal <b>12</b>. When the insulating material <b>14</b> is a body of glass, the feedthrough seal is formed by applying molten glass between the terminal <b>12</b> and the ferrule <b>10</b>, and allowing the molten glass to solidify. This process is generally referred to as “glassing” in the art. A ceramic material can also be included as insulation material, either in place of or together with a glass material.

The noble metal should be carefully selected to ensure that the noble metal film <b>30</b> does not disrupt the stability of the hermetic seal that would be formed between the insulating material <b>14</b> and the terminal <b>12</b> in the absence of the noble metal film <b>30</b>. If the entire terminal <b>12</b> is coated with the noble metal <b>30</b> prior to forming the seal, then the noble metal <b>30</b> must be of the type which can readily react with or diffuse into the metal that forms the terminal <b>12</b>. As a result of proper reactivity and diffusion between the two metals, the insulation material <b>14</b> will be able to wet and react with the material forming the terminal <b>12</b>, and not only with the noble metal film <b>30</b>. Following formation of the seal between the insulating material <b>14</b> and the terminal <b>12</b> extending therethrough, the ferrule <b>10</b> is affixed to the inner surface of the container for the electrical device using any conventional method, and preferably using a welding technique.

An electrical connection between the terminal <b>12</b> and the contact <b>34</b> is secured by a crimping device according to one embodiment of the invention. Turning now to <figref idrefs="DRAWINGS">FIG. 4</figref>, a cross sectional view of a crimping device <b>32</b> is depicted, the crimping device <b>32</b> placing a mechanical force on both the terminal <b>12</b> coated with the noble metal film <b>30</b>, and the contact <b>34</b>. Many known crimping devices can be used in place of the simple crimping mechanism <b>32</b> depicted in <figref idrefs="DRAWINGS">FIG. 4</figref>. Because the terminal <b>12</b> is protected from oxidation due to the presence of the noble metal film <b>30</b>, low resistance crimp connections between the terminal <b>12</b> and conventional contacts such as copper wires or cables may be provided in place of more complicated types of connections. Crimping connections are much less expensive than connections involving alloying or heat joining such as welding. Also, crimping is among the easiest and the least expensive of mechanical methods for joining terminals with other wires or cables. Consequently, the method of the present invention for crimping a noble metal film-coated terminal is a highly advantageous and cost saving option for designing electrical devices that employ feedthroughs to hermetically seal the interior components of the electrical devices.

According to another embodiment, the electrical connection between the terminal <b>12</b> and the contact <b>34</b> is secured by a spring connection. <figref idrefs="DRAWINGS">FIG. 5</figref> depicts a cross sectional view of a spring device <b>36</b>, the spring device <b>36</b> placing a mechanical force on the terminal <b>12</b> coated with the noble metal film <b>30</b>, and electrically coupling the terminal <b>12</b> with the contact <b>34</b>. The spring device <b>36</b> shown in <figref idrefs="DRAWINGS">FIG. 5</figref> is just one of many known spring devices that can be used according to the present invention.

Another embodiment of the invention is depicted in <figref idrefs="DRAWINGS">FIG. 2</figref>. Many of the features depicted in <figref idrefs="DRAWINGS">FIG. 2</figref> are identical to those discussed above. Also, the connection between the terminal <b>12</b> and the contact <b>34</b> using a crimping device <b>34</b>, a spring contact <b>34</b>, or other surface contact is applicable to all embodiments of the present invention, even if not depicted in all of the drawings.

In the embodiment depicted in <figref idrefs="DRAWINGS">FIG. 2</figref>, the terminal <b>12</b> is not coated with a noble metal film <b>30</b> throughout the interior portion of the feedthrough device <b>200</b>. The electrical device is manufactured by first inserting the terminal <b>12</b> into the feedthrough device <b>200</b>, with the noble metal film <b>30</b> being either absent altogether, or absent from at least the regions of the terminal <b>12</b> that will be reacted with the insulating material <b>14</b> to form a hermetic seal. A sealing technique as described above is then performed to seal the insulation material <b>14</b> to the other feedthrough assembly components. Because of the absence of the noble metal film <b>30</b> in the seal region of the feedthrough <b>200</b>, consideration need not be given for potential disruption of the stability of the hermetic seal that is to be formed between the insulating material <b>14</b> and the terminal <b>12</b>. The exposed terminal <b>12</b> exterior to the feedthrough <b>200</b> is coated with the noble metal <b>30</b> after seal manufacture and consequently the noble metal <b>30</b> need not be of the type which can readily react with or diffuse into the metal that forms the terminal <b>12</b>, although such properties may still be advantageous for other reasons. Following formation of the seal between the insulating material <b>14</b> and the terminal <b>12</b> extending therethrough, the ferrule <b>10</b> is affixed to the inner surface of the container for the electrical device using any conventional method, and preferably using a welding technique.

As mentioned above and depicted in <figref idrefs="DRAWINGS">FIG. 2</figref>, the noble metal film <b>30</b> is selectively deposited onto the terminal <b>12</b> in order to avoid having the noble metal in contact with the insulating material <b>14</b> during glassing or any other suitable sealing method. One way that the noble metal film <b>30</b> can be selectively deposited is by employing a method wherein the terminal <b>12</b> is masked with a masking material before the noble metal film <b>30</b> is formed thereon. The mask can be applied to the terminal <b>12</b> using chemical or mechanical masking techniques. The noble metal film <b>30</b> is then formed outside of the areas that will be critical sealing regions, and at least over the region of the terminal <b>12</b> that is to be crimped to the contact <b>34</b>. The masking material is then removed. The selectively coated terminal is then inserted into the feedthrough <b>200</b> and the seal manufacturing method is performed.

Another way that the noble metal film <b>30</b> can be selectively deposited is by performing the seal manufacturing method with a terminal <b>12</b> that is completely free of any noble metal film. Then, the insulative path between the terminal <b>12</b> and the ferrule <b>10</b> or other metal serving as a conductor is isolated using chemical or mechanical masking methods. After isolating the conductors from one another, the noble metal film <b>30</b> is applied at least over the region of the terminal <b>12</b> that is to be crimped to the contact <b>34</b>.

The embodiment of the invention depicted in <figref idrefs="DRAWINGS">FIG. 3</figref> is similar to that of <figref idrefs="DRAWINGS">FIG. 2</figref> in that the terminal <b>12</b> is not coated with a noble metal coating <b>30</b> throughout the interior portion of the feedthrough device <b>300</b>. The method discussed above can be applied to an electrolytic capacitor feedthrough for providing a noble metal film <b>30</b> as a partial coating on the terminal <b>12</b> of the feedthrough <b>300</b>. The feedthrough <b>300</b> includes a capacitor within the feedthrough ferrule <b>10</b>. The capacitive structure may include a multi-layer ceramic structure of annular discoidal shape having several sets of thin, spaced apart, electrically conductive electrode plates <b>20</b> that are separated by thin layers of ceramic dielectric insulating material <b>22</b>. The capacitor also includes first and second mutually isolated electrically conductive exterior and interior termination surfaces <b>24</b> and <b>26</b> and insulative end surfaces <b>28</b>. The alternative methods for selectively coating the noble metal film <b>30</b> over the terminal <b>12</b> are employed in the same manner that they are employed in the embodiment depicted in <figref idrefs="DRAWINGS">FIG. 2</figref>.

Tests performed on the electrical device incorporating the feedthrough apparatus depicted in <figref idrefs="DRAWINGS">FIG. 1</figref> revealed that the noble metal coating does not detrimentally affect the hermeticity of the seal provided by the feedthrough apparatus. Several examples of the configuration of the present invention were tested by first sputter coating approximately 7000 Å of gold, platinum, palladium, ruthenium and rhodium onto respective tantalum wire leads prior to hermetic seal manufacture. The leads were then subjected to a hermetic sealing process that included glassing insulative material onto the noble metal-coated terminals. The terminals were then crimped to standard gold plated copper-beryllium contacts and subjected to standard environmental testing. The testing involved exposing the crimped terminals and contacts to temperatures of 85° F. and 85% relative humidity for long periods of time. All wires were 0.011″ In diameter.

Contact resistance was measure before and after testing. Table 1 below is a summary of the test results.

<tables id="TABLE-US-00001" num="00001"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="8"><colspec colname="1" colwidth="35pt" align="left" /><colspec colname="2" colwidth="21pt" align="center" /><colspec colname="3" colwidth="21pt" align="center" /><colspec colname="4" colwidth="28pt" align="center" /><colspec colname="5" colwidth="28pt" align="center" /><colspec colname="6" colwidth="28pt" align="center" /><colspec colname="7" colwidth="28pt" align="center" /><colspec colname="8" colwidth="28pt" align="center" /><thead><row><entry namest="1" nameend="8" rowsep="1">TABLE 1</entry></row><row><entry namest="1" nameend="8" align="center" rowsep="1" /></row><row><entry /><entry /><entry /><entry>Au</entry><entry>Pt</entry><entry>Pd</entry><entry>Ru</entry><entry>Rh</entry></row><row><entry>Resistance</entry><entry>Ta</entry><entry>Pt</entry><entry>Coated</entry><entry>Coated</entry><entry>Coated</entry><entry>Coated</entry><entry>Coated</entry></row><row><entry>(mhoms)</entry><entry>Wire</entry><entry>Wire</entry><entry>Ta Wire</entry><entry>Ta Wire</entry><entry>Ta Wire</entry><entry>Ta Wire</entry><entry>Ta Wire</entry></row><row><entry namest="1" nameend="8" align="center" rowsep="1" /></row></thead><tbody valign="top"><row><entry /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="8"><colspec colname="1" colwidth="35pt" align="left" /><colspec colname="2" colwidth="21pt" align="char" char="." /><colspec colname="3" colwidth="21pt" align="char" char="." /><colspec colname="4" colwidth="28pt" align="char" char="." /><colspec colname="5" colwidth="28pt" align="char" char="." /><colspec colname="6" colwidth="28pt" align="char" char="." /><colspec colname="7" colwidth="28pt" align="char" char="." /><colspec colname="8" colwidth="28pt" align="char" char="." /><tbody valign="top"><row><entry>Intl. Ave.</entry><entry>146</entry><entry>7.52</entry><entry>23.8</entry><entry>10.73</entry><entry>9.4</entry><entry>10.16</entry><entry>10.87</entry></row><row><entry>Std. Dev.</entry><entry>93.2</entry><entry>0.19</entry><entry>9.03</entry><entry>0.64</entry><entry>0.69</entry><entry>0.86</entry><entry>0.85</entry></row><row><entry>Shift Ave.</entry><entry>104.3</entry><entry>40.6</entry><entry>59.1</entry><entry>49.17</entry><entry>0.78</entry><entry>−0.21</entry><entry>2.17</entry></row><row><entry>(post test)</entry></row><row><entry>Std. Dev.</entry><entry>144.6</entry><entry>0.37</entry><entry>54.2</entry><entry>101.5</entry><entry>1.5</entry><entry>3.21</entry><entry>1.85</entry></row><row><entry namest="1" nameend="8" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

The test results that are summarized in Table 1 show that significant improvements in both initial contact resistance and resistance shift resulted from coating tantalum wires with various noble metals, when compared with a contact involving bare tantalum wire. The improvements were especially significant when the noble metal film was a palladium, ruthenium, or rhodium coating. Similar improvements result from any of the noble metals as coatings of other refractory metal terminals.

Turning now to <figref idrefs="DRAWINGS">FIGS. 6 and 7</figref>, another embodiment of the feedthrough assembly with metal coated leads according to the present invention is illustrated in the environment of a pacing device <b>400</b>, although the use for the illustrated feedthrough assembly is in no way limited to such a device. Many of the features depicted in <figref idrefs="DRAWINGS">FIGS. 6 and 7</figref> are identical to those discussed above. In <figref idrefs="DRAWINGS">FIGS. 6 and 7</figref>, the feedthrough terminal <b>12</b> coated with the noble metal film <b>30</b> and is securely engaged with a spring contact <b>36</b>. The spring contact <b>36</b> is welded or otherwise joined to a conductive socket housing <b>42</b> which laterally surrounds the spring contact <b>36</b>. The socket housing <b>42</b> is welded or otherwise secured to a flex circuit <b>46</b> which includes circuitry laminated within an insulative material. The spring contact <b>36</b> and the socket housing <b>42</b> couple the terminal <b>12</b> with selected circuitry within the flex circuit <b>46</b>.

The ferrule <b>10</b> is also coated with a conductive metal film <b>48</b> according to this embodiment. The film <b>48</b> enables an electrical contact to be electrically coupled to, and mechanically engaged with, the ferrule <b>10</b> using a surface contact including but not limited to the crimping connection or the spring contact discussed above. The construction shown in <figref idrefs="DRAWINGS">FIGS. 6 and 7</figref> includes a spring contact <b>44</b> that securely engages with the film <b>48</b> and electrically couples the ferrule <b>10</b> with selected circuitry within the flex circuit <b>46</b>. The conductive metal film <b>48</b> can be formed from any metal that is less easily oxidized than the ferrule <b>10</b>, but is preferably a noble metal or an alloy of noble metals.

Suitable noble metals include gold, platinum, palladium, rhodium, ruthenium, and iridium, although titanium, niobium and alloys of titanium or niobium are preferred. Just like the metals used for the film <b>30</b> that coats the feedthrough terminal <b>12</b>, these metals and alloys thereof protect the ferrule from hot, humid, or liquid environments. The protection provided by the noble metals and alloys thereof decrease the contact resistance, and therefore increase the stability of surface connections between a contact and the ferrule <b>10</b>. The film <b>48</b> is applied by DC magnetron sputtering or RF sputtering in an exemplary embodiment of the invention, although other conventional techniques may be used such as chemical vapor deposition, cladding, vacuum depositing, painting, other types of sputtering, etc. The film <b>48</b> is deposited at a minimum thickness of about 100 Å, and preferably is at a thickness ranging from about 3000 Å to about 7000 Å.

While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.